| With the market demand of automobile tire pressure monitoring system,pressure sensors have been highly desired. Capacitive pressure sensor with simpleand robust structure、 high sensitivity, which is widely used in tire pressuremonitoring system.The capacitive pressure sensor can be divided into touch mode and no-touchmode. Touch mode capacitive pressure sensor has distinct advantages, such asnear-linear output characteristics, over-range pressure and robust structure thatmake it capable to withstand harsh environment. At present, compared with othercountries, there is comparatively insufficient in research and fabrication of touchmode capacitive pressure sensor in our country. Therefore, touch mode capacitivepressure sensor suitable for motor tire pressure monitoring system is made withMEMS process technology in this subject.A new type of touch mode capacitive pressure sensor is presented, which has aspherical crown shape of a circular cavity in bottom fixed plate. A flexiblediaphragm with a composite membrane structure greatly improves the robustnessand reliability of the movable plate, while increasing its pressure-capacitancelinearity. The cavity design of fixed plate is the spherical crown shape. Underoutside pressure, the classics process of contact between the bipolar plates waschanged and sensor sensitivity and linearity was improved consequentially.Secondly, because it is used in tire pressure monitoring system (100-800kPa), thedesign process requires to analyze and to discuss how the different diaphragm sizeand depth of cavity parameters have impact on touch mode capacitive pressuresensor. ANSYS is used to simulation analyze and verify the structure.The structure with its fabrication process has been designed based on thetheoretical analysis. The key processes are silicon direct bonding technology、chemical grinding and chemical mechanical polishing technology. This sensor,which it can meet the using of tire pressure monitoring system, has a goodapplication value. |
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